Due to the development of radio communication technologies, a high-performance filter is required in a low-cost and high-performance wireless communications transceiver system. A dielectric filter is widely used in various communications systems because of its small size, low loss, and high selectivity. The dielectric filter includes a cavity, a dielectric resonator fastened inside the cavity, a cover, and an adjusting screw. The adjusting screw is used to adjust a frequency and bandwidth of the dielectric filter. A dual-mode dielectric filter is a type of dielectric filter. The dielectric filter is designed by using a dielectric material (such as ceramic) that is characterized by a low loss, a high dielectric constant, a small frequency temperature coefficient, a small coefficient of thermal expansion, and a capability of bearing high power, and the like. Generally, the dielectric filter may be formed by ladder-shaped lines with several cuboid resonators that are lengthwise connected in series or in parallel at different levels. The dielectric filter is characterized by a low insertion loss, a capability of bearing high power, and narrow bandwidth; the dielectric filter is especially suitable for filtering of 900 MHz, 1.8 GHz, 2.4 GHz, and 5.8 GHz frequencies; the dielectric filter may be applied to area coupled filtering of a portable phone, an automobile phone, a wireless headset, a wireless microphone, a radio station, a cordless telephone set, or an integrated transceiver duplexer. The dual-mode dielectric filter is a filter that uses a dual-mode dielectric resonator. One dual-mode dielectric resonator can simultaneously operate in two working modes, and one working mode corresponds to one resonance frequency; therefore, the dual-mode dielectric resonator can simultaneously operate at two resonance frequencies. The working mode refers to a pattern of an electric field or a magnetic field in which the resonator works. For the dielectric resonator, its working modes usually include a TM (Transverse Magnetic) mode, a TE (Transverse Electric) mode, or an HE (Hybrid Electromagnetic) mode (that may include two working modes of the HE, and is also referred to as an HE dual-mode). Generally, the dual-mode dielectric filter includes the HE dual-mode. In the dual-mode dielectric filter, the adjusting screw is disposed around the cavity of the dual-mode dielectric filter, which does not facilitate adjustment of the dual-mode dielectric filter and assembling of other components.